Organic Light Emitting Diodes (OLED) refer to the technology of organic semiconductor material emitting light under the influence of the electric field. OLED shows promising prospects in flat panel display and lighting because of its various advantages such as self-luminescence, all solid state, low driving voltage, high efficiency, fast response, wide viewing angle, simple manufacturing process and capacity of large area and flexible display.
Generally a known OLED device structure includes a hole transporting layer, a light emitting layer, an electron transporting layer and an electron injection layer. To improve the luminous efficiency and to prolong the lifetime of the OLED device, various hole transport materials have been studied and used. For example, triarylamine, which was discovered in early age of photocopy developing technology, has high carrier mobility. However, triarylamine is not conducive to the preparation of organic electroluminescent devices for its low glass transition temperature and poor film-forming properties. Take pentacene compounds as another example, they exhibit high carrier mobility, but such substances have high HOMO level, and do not have stable redox repeatability, which results in short lifetime of the organic electroluminescent devices prepared.